The development of any tissue requires a temporally regulated series of events, including the orderly production of different cell types. The development of the vertebrate retina is no exception, with a conserved order of production of neurons and glia. The mechanism(s) used to drive this order is unknown. The retinal progenitor cells that produce this order are multipotent throughout development, but have not been shown to be totipotent throughout development. They thus might differ in the types of cells that they can make at any one time. Current data support such a model, wherein retinal progenitor cells undergo temporally regulated changes in their competence to make the distinctive types of neurons over time. It is of interest to define the gene expression history of retinal progenitor cells, and correlate this with the types of progeny cells that they produce. In addition, it is likely that different types of progenitor cells are defined by their transcription factor networks. It is thus also of interest to learn about the functions of the transcription factors that define these temporal states. Therapies that enable stem cells to replace dying or diseased cells will require the instruction of stem cells for production of the proper cell types, e.g. rod and cone photoreceptor cells. In addition, when development does not proceed normally, due to genetic or environmental influences, blindness is a frequent outcome. An understanding of the mechanisms that direct cell fates will greatly enable the instruction of stem cells, and/or other types of therapies that can address developmental abnormalities. PUBLIC HEALTH RELEVANCE: Therapies that enable stem cells to replace dying or diseased cells will require the instruction of stem cells for production of the proper cell types, e.g. rod and cone photoreceptor cells. In addition, when development does not proceed normally, due to genetic or environmental influences, blindness is a frequent outcome. An understanding of the mechanisms that direct cell fates will greatly enable the instruction of stem cells, and/or other types of therapies that can address developmental abnormalities.